Heating flange for preheating air in an intake line of an internal combustion engine

ABSTRACT

The present invention relates to a heating flange, in particular for preheating air in an intake line leading to an internal combustion engine. The heating flange comprises at least one heating element for heating the air flowing past said heating element, and a body for mechanically holding and electrically contacting said heating element. For providing an improved heating flange, which is used in particular for preheating air in an intake line leading to an internal combustion engine and which guarantees fast heating of the intake air as well as increased robustness and simplified mounting, said body comprises a fastening bow having a substantially U-shaped cross-section, and said heating element comprises at least one substantially U-shaped meander loop which is fixedly connected to the base of said fastening bow.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention generally relates to a heating flange andmore specifically to a heating flange for preheating air in an intakeline leading to an internal combustion engine.

[0003] 2. Description of the Related Art

[0004] Presently, for instance in diesel engines, the use of pre-swirlchambers is normally dispensed with to a large extent, and thepreheating time can be reduced markedly by means of direct fuelinjection under high pressure. In the case of lorries, preheating isnormally dispensed with completely, and the temperature required forigniting the fuel is here achieved by strong air compression. Thistechnique depends, however, to a high degree on the temperature and thedensity of the combustion air taken in. At low temperatures, theelectric starter must rotate the engine until a temperature rise hastaken place in the combustion chambers due to a plurality of compressionprocesses and until ignition of the fuel is possible. Vehicles which areoften operated at low temperatures and low air pressures are thereforeequipped with systems heating the intake air prior to the startingoperation. At present, such systems operate e.g. on the basis of gasburners.

[0005] These systems are, however, disadvantageous insofar as thecontent of the oxygen required for the future combustion of the fuel isreduced and that, in addition, the technical expenditure iscomparatively high.

[0006] Hence, alternative electric heating systems are used, this kindof systems being disclosed e.g. in DE 100 26 339 A1 or in DE 195 15 533C2. In particular the device for preheating air in an intake lineleading to a diesel engine, which is shown in DE 100 26 339 A1 and whichis provided with a switching unit controllable by means of asemiconductor device operating in a wear-free manner, permits theheating flange to be switched on and off an arbitrary number of timesand at very short intervals, i.e. with comparatively high frequencies.Hence, the power of the heating flange can be adapted to the warm-upconditions of the internal combustion engine almost steplessly.

[0007] This preheating device is, however, problematic insofar as, dueto the high currents flowing (up to 400 ampere and more), the heatingflange has to satisfy very special requirements with respect to currentendurance, temperature resistance and mechanical stability.

SUMMARY OF THE INVENTION

[0008] An improved heating flange, in particular for preheating air inan intake line leading to an internal combustion engine, is providedwhich guarantees fast heating of the intake air as well as increasedrobustness and simplified mounting.

[0009] In one embodiment, a heating flange, in particular for preheatingair in an intake line leading to an internal combustion engine, isprovided, said heating flange comprising at least one heating elementfor heating the air flowing past said heating element. The heatingflange further comprises a body for mechanically holding andelectrically contacting said heating element. The body has a fasteningbow having a substantially U-shaped cross-section, and the heatingelement comprises at least one substantially U-shaped meander loop whichis fixedly connected to the base of the fastening bow.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] The accompanying drawings are incorporated into and form a partof the specification for the purpose of explaining the principles of theinvention. The drawings are not to be construed as limiting theinvention to only the illustrated and described examples of how theinvention can be made and used. Further features and advantages willbecome apparent from the following and more particular description ofthe invention which is illustrated in the accompanying drawings,wherein:

[0011]FIG. 1 is a perspective representation of a heating flangeaccording to a first advantageous embodiment;

[0012]FIG. 2 illustrates a side view of the heating flange of FIG. 1;

[0013]FIG. 3 is a side view of the heating flange of FIG. 2, rotated by90°;

[0014]FIG. 4 illustrates a top view of the heating flange of FIG. 1;

[0015]FIG. 5 illustrates a perspective representation of a heatingflange according to a second advantageous embodiment;

[0016]FIG. 6 illustrates a side view of the heating flange of FIG. 5;

[0017]FIG. 7 is a side view of the heating flange of FIG. 6, rotated by90°;

[0018]FIG. 8 is a top view of the heating flange of FIG. 5;

[0019]FIG. 9 shows a perspective view of a heating flange according to athird advantageous embodiment;

[0020]FIG. 10 is a time diagram of the electric power fed to the heatingflange;

[0021]FIG. 11 is a circuit diagram of an electric switching means forcontrolling two heating elements;

[0022]FIG. 12 shows a state diagram of the control status of the twoheating elements as well as of the whole power fed.

DETAILED DESCRIPTION OF THE INVENTION

[0023] The illustrated embodiments of the present invention will bedescribed with reference to the figure drawings wherein like elementsand structures are indicated by like reference numbers.

[0024] Referring now to the drawings and in particular to FIG. 1, aperspective representation of a heating flange according to the presentinvention in accordance with a first advantageous embodiment is shown.The heating flange 100 comprises a body 101 which is adapted to bemounted on an intake line in such a way that the two heating elements102 and 104 are immersed in the air current to be heated, said intakeline leading to an internal combustion engine. The heating elements 102,104 are heated by an electric current flowing through same, whereby theair flowing around said heating elements will be heated.

[0025] In the embodiment shown, each of the two heating elements 102,104 is defined by a substantially U-shaped meander loop. Such meanderheating elements are particularly suitable for heating gaseous media,since, due to the direct contact with the heating conductor, a good heattransfer is given. The two heating elements 102, 104 are mechanicallystabilized by a fastening bow 106. For secure fastening, the heatingelements 102, 104 are connected to the base of the substantiallyU-shaped fastening bow 106 via riveted joints. In addition, each heatingelement 102, 104 is connected to the voltage supply.

[0026] The heating elements 102, 104 are electrically insulated from asupport element 109, which is produced e.g. from aluminum, as well asfrom the fastening bow 106 by means of micanite boards 110, 112. A cover108, which can preferably be produced from plastic material, serves toseal a respective opening in the intake line. The cover 108 hasadditionally integrated therein the connecting leads for power supply aswell as the control electronics. A pin for the positive voltage 114, apin for connection to ground 116 as well as the connecting cable 118 forthe control are extended outwards. The two power-supply pins 114, 116have a thread so that the cover 108 can be pressed onto the aluminumsupport element 109 by means of two suitable nuts.

[0027] In the installed condition of the heating flange, the cover 108is sealed from the intake line through a flat gasket 128, which consistse.g. of silicon, in the present embodiment. It is, however, alsopossible to provide a double O-ring seal.

[0028] Since the heating elements 102, 104 are fixed in a mechanicallyrigid manner in the area of the support element 109 as well as in thearea of the base of the fastening bow 106, it must be guaranteed that adefined change of position of the heating elements 102,104 relative tothe fastening bow 106 will take place in the case of different thermalexpansions of the heating elements 102, 104. For this purpose, the legsof the U-shaped meander loops of the heating elements 102,104 can beangled such that bends 120 are formed, which guarantee a directed,predetermined change of position when said legs increase in length. Inthis way, it can be guaranteed that the legs of the meander loops of theheating elements will move towards each other or come into contact withthe fastening bow 106, whereby an electric short circuit will be causedin an extreme case. This resilient construction of the heating elementswill also prevent said heating elements from breaking, e.g. due toengine vibrations.

[0029] As indicated by the arrow 122, it has to be assumed that the mainflow direction of the air is a direction transversely to the U-shapedcross-section of the fastening bow 106. The legs of the fastening bow106 are, however, provided with openings 124 permitting the air to beheated to flow in also in a direction transversely to the main flowdirection 122. In the embodiment shown, the fastening bow 106 isconductively connected to the aluminum block 126 of the cover 108 andconnected to ground. The insulation from the heating elements 102,104 iseffected by means of the insulation board 112.

[0030] Various views of the heating flange 100 according to theembodiment shown in FIG. 1 can be seen in FIGS. 2 to 4.

[0031]FIG. 5 shows a perspective representation of a second advantageousembodiment in the case of which each heating element 102, 104 consistsof two essentially U-shaped meander loops. In this embodiment, eachheating element 102, 104 has a total of four heat-emitting legs immersedin the air current. Also in this embodiment, it will be expedient toprovide bends 120 for obtaining a defined deflection in the case ofthermal expansion.

[0032] When seen in a direction transversely to the U-shaped fasteningbow 106, the two heating elements 102, 104 are arranged one behind theother and, in addition, displaced relative to one another in a directionparallel to the U-shaped cross-section of the fastening bow 106. Thecurrent of the air to be heated can, in this way, flow around thelargest possible surface of the two heating elements 102, 104. Also inthis embodiment, the heating elements 102, 104 are insulated from thebase of the fastening bow 106 as well as from the aluminum block 126 ofthe cover 108 through micanite boards 110 and 112. The mechanical fixingof the heating elements 102, 104 as well as the fixing of the insulationboard 110 to the base of the fastening bow 106 is effected by means ofrivets 130.

[0033] FIGS. 6 to 8 show various views of the heating flange 100according to the embodiment shown in FIG. 5.

[0034] In FIG. 9 a perspective view of a heating flange 100 according toa third advantageous embodiment is shown. Other than in the case of theembodiments shown hereinbefore, the fastening bow 106 of this embodimentis not conductively connected to the aluminum block 126, but it iselectrically insulated therefrom by an insulation 112. Since, in thisembodiment, it is no longer necessary to electrically insulate the baseof the U-shaped cross-section of the fastening bow 106 from thecurrent-carrying heating elements 102, 104, it will suffice to providewelded joints 132 at the fastening bow 106 so as to mechanically fix theheating elements 102, 104, whereby the production can be facilitated andreduced in price still further. Although FIG. 9 shows an embodimentcorresponding to FIG. 1 with only one meander loop per heating element102, 104, it is, of course, also possible to use this embodiment forheating elements comprising more than one meander loop. The rivets 130as well as the insulation 110 can be dispensed with in any case.

[0035]FIG. 10 shows exemplarily a typical time profile of the heatingpower when a diesel engine is being started. Prior to the startingmoment 134, which occurs e.g. after three seconds, the intake air ispreheated with 100% heating power. By controlled intermittent switchingoff of the heating power supply, a pulse width modulation can beachieved in a simple manner and, when the engine has been started, theair can still be heated for a predetermined period of time with a lowheating power (e.g. 25% to 50%). This will make sense e.g. in caseswhere outdoor temperatures are very low, and in the example shown suchheating is effected for a period of 20 seconds after switching on of theheating. The maximum electric heating power is in the range of approx.10 kW. Due to this high power, particularly fast heating of the intakeair prior to starting of the engine is guaranteed.

[0036]FIG. 11 shows a circuit diagram of the electronic control for aheating flange with two heating elements. The use of two heatingcircuits and of fast, wear-free semiconductor switches 136, 138, 140 and142 offers the possibility of controlling the heating power continuouslyand of permitting in this way a possibly necessary heating of the intakeair with little power also when the engine is in operation.

[0037] When, as shown in FIG. 11, two semiconductor switching elementsare used, which are in series with a heating element, the function ofthe semiconductors can be examined. Hence, a possibility of switchingoff is guaranteed and a fuse element can be dispensed with. If thecurrent through a heating element exceeds the maximum current-carryingcapacity of a MOSFET, it is also possible to connect a plurality ofsemiconductor switches in parallel.

[0038] The control electronics comprises a micro controller whichprevents overloading of the heating circuits, supervises the function ofsaid heating circuits and produces an indication signal in the case ofmalfunction. In addition, the electronics is capable of effectingcontrolled switching on of the heating circuits, if permanent excessvoltages occur in the onboard power supply, so as to subject the onboardpower supply to an electric load, whereby the excess voltage will bereduced. Optional temperature detection can be carried out via thetemperature sensor 146 and, on the basis of this information, controlledintake-air preheating can be executed by means of the micro controller144. Instead of the four semiconductor switches 136 to 142 shown, it isalso possible to use a suitable single MOS field effect transistor.

[0039]FIG. 12 shows the variation with time of the control signals forthe two heating elements and the resultant time profile of the on-offphases of the load. The two heating elements can, for example, beswitched on and off in such a way that heating element 2 (cf. curve 150)is switched off, when heating element 1 (according to curve 148) hasjust reached half of its “ON” phase. The load is only switched on whenboth heating elements are switched on (curve 152). Such a temporallydisplaced control of the two heating elements will be advantageous, ifit is e.g. desired to reduce the electromagnetic disturbances caused bythe heating elements.

[0040] Various embodiments as described above may advantageously achievea particularly good heat transfer between the heating element and theair to be preheated as well as a particularly robust and shake-proofconstruction of a heating flange, when the body comprises a fasteningbow having a substantially U-shaped cross-section, and when the heatingelement comprises at least one substantially U-shaped meander loop whichis fixedly connected to the base of said fastening bow. In this way, theheating element is mechanically protected in the best possible manner onthe one hand and, on the other hand, the air to be heated flows aroundthe largest possible area of the surface of said heating element. On thebasis of this robust structural design, the heating element is resistantto the strong vibrations caused by the engine. Another advantage of theheating flange according to the present invention is that it can bemounted easily and therefore at a moderate price due to a small numberof electrical and mechanical interfaces.

[0041] According to an advantageous embodiment, the heating element iselectrically insulated from the fastening bow at the base of said bow.In this way, it is possible that the fastening bow has connected theretoa potential, e.g. ground, which is different from the potential of theheating element.

[0042] A particularly low-priced and effective possibility of realizingsuch an electric insulation is the arrangement of a substantiallyrectangular board consisting of an electrically insulating material,preferably mica, micanite or ceramics, between the heating element andthe base of the fastening bow. When the material micanite is used forthis purpose, this material offers the advantage of high dielectricstrength (higher than 20 kV/mm), an admissible use temperature of 600°C. to 900° C., a very small water-absorbing capacity (less than 1%) aswell as a good thermal conductivity. In addition, this material can begiven the desired shape in a particularly easy way.

[0043] A method of establishing a connection between the fastening bowand the heating element, which is particularly safe under the roughenvironmental conditions to which said connection will be subjected whenused in motor vehicles, is riveting.

[0044] Another very reliable connection between the heating element andthe fastening bow is a welded joint, which is, in addition, particularlyeasy to produce and which saves on material.

[0045] Materials which are often used for heating elements are ferriticiron-chromium-aluminum alloys. The alloy Kanthal D®, a registeredtrademark of the firm of Kanthal AB, has e.g. a temperature stability ofup to 1,300° C. and is frequently used for heating tasks in householdsas well as for industrial applications.

[0046] According to an advantageous embodiment, the body of the heatingflange additionally comprises a cover through which the heating flangecan be connected to the intake line. This permits a particularly simplemounting of the heating flange in the intake line. This cover can besealed from the intake line e.g. by a flat gasket or by double O-ringsarranged on said cover. Due to the fact that, in this embodiment, thefastening bow with the heating elements is fully immersed in the aircurrent of the intake line, the air can be heated in a particularlyeffective manner.

[0047] According to another advantageous embodiment, the fastening bowis connected to the cover in an electrically conductive manner. Both thefastening bow and the cover can be connected to ground in this way and,consequently, they will not act an as antenna for the emission ofpossible electromagnetic disturbances caused by the control of theheating elements.

[0048] In an alternative embodiment, the fastening bow is electricallyinsulated from the cover. This offers the advantage that an electricinsulating layer is no longer necessary between the fastening bow andthe heating element, whereby the production can take place with lessexpenditure of time and material.

[0049] Normally, the material of the U-shaped meander loop of theheating element has a temperature coefficient which is different fromthat of the material used for producing the fastening bow. In addition,much higher temperatures are reached at the heating element. In order tobe able to compensate the different degrees of expansion of thefastening bow and of the heating element when the heating flange is inoperation, the legs of the U-shaped meander loop of the heating elementare angled at least once in the freestanding area encompassed by the aircurrent. This has the effect that the heating element is resilientlysupported in the fastening bow so that said heating element is reliablyfixed even in the case of strong vibrations and so that a deformation ina defined direction will be possible under the influence of heat.

[0050] According to an advantageous further development of the presentinvention, the heating flange comprises two heating elements which arearranged such that they are displaced relative to one another in adirection transversely to the U-shaped cross-section of the fasteningbow. These two heating elements offer the advantage of an increasedheating power and of a larger surface for heating the air flowingthrough.

[0051] In order to provide a heating element pattern which extendsthrough the air volume in the most effective manner, the legs of themeander loop of the two heating elements can be angled in oppositedirections.

[0052] For obtaining a particularly good heat transfer, the fasteningbow can be provided with openings formed in the flanks thereof and usedfor allowing the air to be heated to flow in transversely to the openingof the U-shaped cross-section.

[0053] According to an advantageous embodiment, the heating flange isprovided with a switching means for switching the electric power at theheating element on and off. With the aid of such a switching means, theelectric power can be supplied to the heating element according torequirements and a pulse width modulation for controlling the heatingpower supply can be realized e.g. by defined switching on and off.

[0054] When a switching means comprising a semiconductor device isprovided for switching on and off, this embodiment offers the advantagethat the semiconductor device switches reliably and in a wear-freemanner, that must higher switching frequencies can be realized and thatthe size of the switching means in its entirety can be markedlyminiaturized in comparison with arrangements comprising a relay.

[0055] When at least two separately controllable heating elements areprovided on the heating flange, which are each connected to a respectiveswitching means for switching the electric power supply on and off, thetwo heating elements can be controlled independently of one another,whereby the flexibility of the control will be increased considerably.

[0056] It is, for example, possible to supply power to the two heatingelements in a time-shifted manner in such a way that electromagneticdisturbances, which are caused by switching the heating elements on andoff, will cancel one another when averaged over time. In view of thefact that the disturbance energy stored in the line inductance isproportional to the current flowing, the electromagnetic disturbancewill be reduced accordingly by the division of the currents.

[0057] A micro controller used for controlling the power supply to theheating element guarantees flexibly adjustable heating characteristicswhich are adapted to the engine properties in the best possible way. Inaddition, the microcontroller can take over the following functions:

[0058] safety cut-off when a maximum temperature or maximum power-onperiod has been reached,

[0059] supervision of the semiconductor switching elements,

[0060] triggering safety cut-off devices,

[0061] determining the current flowing, and detecting transitionresistances in this way,

[0062] diagnostic functions

[0063] reducing the electromagnetic radiation by suitable controlalgorithms.

[0064] When at least one temperature sensor is provided for detectingrespective temperature values occurring, e.g. temperature values of theair to be heated, but also the outdoor temperature or the like, thissolution offers the advantage that not only an open-loop control butalso a closed-loop control of the heating process can be carried out andthat said heating process can, consequently, be executed in aparticularly power-saving and efficient mode. Such a temperature sensorcan also by used for protecting the electronics against overheating.

[0065] While the invention has been described with respect to thephysical embodiments constructed in accordance therewith, it will beapparent to those skilled in the art that various modifications,variations and improvements of the present invention may be made in thelight of the above teachings and within the purview of the appendedclaims without departing from the spirit and intended scope of theinvention.

[0066] In particular, it is also possible to use an optical sensor whichdetects infrared light. By means of such an optical sensor, it would bepossible to supervise the glowing up of the heating elements and tocontrol it accordingly. This would permit a maximum power supply, whichwould be adapted to the air current in question, and it would not benecessary to detect the air current by complicated means and measures.Furthermore, a safe mode of operation will be possible, if the aircurrent should fail to arrive.

[0067] In addition, those areas in which it is believed that thoseordinary skilled in the art are familiar have not been described hereinin order not to unnecessarily obscure the invention described herein.

[0068] Accordingly, it is to be understood that the invention is not tobe limited by the specific illustrated embodiments but only by the scopeof the appended claims.

What is claimed is:
 1. A heating flange, in particular for preheatingair in an intake line leading to an internal combustion engine, saidheating flange comprising at least one heating element for heating theair flowing past said heating element, and a body for mechanicallyholding and electrically contacting said heating element, wherein saidbody comprises a fastening bow having a substantially U-shapedcross-section, and the heating element comprises at least onesubstantially U-shaped meander loop which is fixedly connected to thebase of said fastening bow.
 2. The heating flange according to claim 1,wherein the heating element is electrically insulated from the fasteningbow at the base of said bow.
 3. The heating flange according to claim 2,wherein a substantially rectangular board consisting of an electricallyinsulating material, preferably mica, micanite or ceramics, is arrangedbetween the heating element and the base of the fastening bow.
 4. Theheating flange according to claim 1, wherein the heating element isriveted to the fastening bow at the base of said bow.
 5. The heatingflange according to claim 1, wherein the heating element is welded tothe fastening bow at the base of said bow.
 6. The heating flangeaccording to claim 1, wherein the heating element is adapted to beproduced from a ferritic iron-chromium-aluminium alloy, preferablyKanthal D.
 7. The heating flange according to claim 1, wherein the bodyof the heating flange additionally comprises a cover through which theheating flange can be connected to the intake line.
 8. The heatingflange according to claim 7, wherein the fastening bow is connected tothe cover in an electrically conductive manner.
 9. The heating flangeaccording to claim 7, wherein the fastening bow is electricallyinsulated from the cover.
 10. The heating flange according to claim 1,wherein the legs of the U-shaped meander loop of the heating element areangled at least once in the freestanding area encompassed by the aircurrent.
 11. The heating flange according to claim 1, wherein theheating flange comprises a first and a second heating element, saidheating elements being arranged such that they are displaced relative toone another in a direction transversely to the U-shaped cross-section ofthe fastening bow.
 12. The heating flange according to claim 11, whereinthe legs of the meander loop of the first heating element are angled inthe freestanding, air current-encompassed areas thereof in a directionopposite to the direction in which the legs of the meander loop of thesecond heating element are angled.
 13. The heating flange according toclaim 1, wherein the fastening bow is provided with openings formed inthe flanks thereof and used for allowing the air to be heated to flow intransversely to the opening of the U-shaped cross-section.
 14. Theheating flange according to claim 1, wherein a switching means isprovided for switching the electric power at the heating element on andoff.
 15. The heating flange according to claim 14, wherein the electricswitching means comprises at least one semiconductor device.
 16. Theheating flange according to claim 15, further comprising at least twoseparately controllable heating elements which are each connected to arespective switching means for switching the electric power supply onand off.
 17. The heating flange according to claim 16, wherein theheating elements have power supplied thereto in a time-shifted manner.18. The heating flange according to claim 1, wherein the power supply ofthe heating element is controlled by means of a micro controller. 19.The heating flange according to claim 1, further comprising at least onetemperature sensor for detecting respective temperature valuesoccurring, preferably temperature values of the air to be heated.